In the measurement of the caliper of lightweight paper, care must be taken to avoid marking or ripping the paper. This is especially critical when slight flaws are present in the sheet material which must be accommodated by the thickness gauge. In addition to being tolerant to flaws, the measuring gauge or thickness gauge should be tolerant to ripples and curvatures in the paper, especially in the cross-direction. Lastly, a thickness gauge should accommodate the so-called passline of the moving paper which may vary as much as one-half inch.
One type of thickness gauge which meets several of the above requirements is shown in U.S. Pat. No. 4,929,895 in the name of Pekka M. Typpo, the present inventor and assigned to the present assignee. This patent utilizes a pair of flexibly mounted air bearings. However, it is still desirable to provide further improvements in a thickness gauge so that lighter papers can be measured with greater accommodation of various flaws, ripples and curvatures of the paper.